1. Field of the Invention
The present invention relates to a fluidization and conveyor arrangement for electrostatic powder coating devices.
2. Description of the Related Art
In electrostatic powder coating devices, fluidized powder, in the form of an air-powder mixture, must be supplied to the applicators, or powder guns, with an optimally uniform distribution of powder particles in the powder-air stream. The powder is supplied in original packaging (such as sacks, barrels, boxes or plastic containers) and is subsequently poured into specific preparation containers (such as dressing or processing containers). Preparation containers typically have an inside floor, configured as a porous plate or fluidization plate, an intake of compressed air, and an air discharge line. Upon the admission of compressed air into the preparation container, the powder is deagglomerated by contact with the fluidization plate, and is fluidized into an air-powder mixture. The air-powder mixture is then removed from the fluidized bed and conveyed to the powder gun. In known devices, the loosening and fluidization of the powder is frequently facilitated by vibrators.
One example of such a preparation container is discussed in German Patent 36 11 039. A considerable amount of time is needed to clean such a container. Such a time expenditure is disadvantageous, particularly when frequent changes in the powder color are necessary. One effort to obviate this problem is discussed in European Patent 0 184 994, which proposed removing the powder directly out of the original packaging by suctioning. Such removal can be accomplished by using a lance-like powder extraction device, composed of a suction tube and a plurality of compressed air conduits, that is lowered into the opened original packaging. The powder extraction device fluidizes the powder in the vicinity of the intake orifice of the suction tube, by which the fluidized powder is suctioned out of the packaging. For further loosening of the powder, the original packaging can be placed on a vibrator. Such a powder extraction device eliminates the need for a special preparation container, such that changes in color can be easily and readily implemented. However, as such a device only provides for fluidization of the powder in the region of the suction tube, the powder distribution in the departing powder-air stream is not as uniform as in a powder-air stream derived from a special preparation container having a fluidization plate.